The commit efab27afbf02743a3a2582e9a111eb1b7d985b26 in libvirt uses
/dev/%s for logical pools, change the tests to accommodate it.
(crobinso: additional fix to work with older libvirt)
This base connection object will be used to simplify the API in various
places, reduce libvirt API calls, and better share code between virtinst
and virt-manager. For now it just centralizes connection opening.
This also exposed various places where our handling for older libvirt
was busted, so raise our minimum host version to 0.6.0, the first
version that supports threaded client requests.
